Over 17 million Americans are disabled as a result of their arthritis, making arthritis the major cause of disability in the US. Knee osteoarthritis (knee OA) and rheumatoid arthritis (RA) are major causes of arthritis- related disability. This proposed study addresses an important public health problem: how to reduce disability progression for persons with knee OA and RA. This study will test the effectiveness of the Physical Activity Management (PAM) intervention to prevent disability progression in patients with knee OA and RA. The proposed research is integrated into the NIH- funded PAM Randomized Clinical Trial, which provides efficiency in study logistics and economic savings. The PAM Trial is enrolling 240 patients with knee OA and 240 patients with RA. The PAM intervention is a tailored patient self-management intervention supplementing physician counseling to increase physical activity behavior. The control group is physician physical activity counseling alone. Semi-annual funded PAM Trial assessments include pain, function, and state-of-the art physical activity measurement via accelerometer. The proposed study requests funds to add measurements of disability and disability progression compared to baseline levels and to assess the attainment of recommended physical activity guidelines in PAM Trial participants based on objective, funded accelerometer monitoring. The proposed study is designed to objectively and definitively address the following aims at minimal cost: 1. Use the methodologically strong framework of a randomized clinical trial to determine if the PAM compared to control intervention is effective in preventing disability progression and to determine if this effect is due to improved frequency at which persons with knee OA and RA meet recommended physical activity guidelines. 2. Measure the effect of attaining recommended public health physical activity guidelines, such as those recommended by the US Surgeon General, to reduce disability progression, functional decline, and pain. We also investigate a physical activity dose-response relationship with those outcomes. The PAM intervention offers a potentially effective method to reduce disability progression by promoting physical activity at the health systems level. Motivating persons with arthritis to increase physical activity is a stated objective of Healthy People 2010. If a heath systems intervention such as PAM reduces disability, a key driver of health care costs in arthritis, this finding has important public policy and insurance reimbursement implications for the containment of rising medical costs. Furthermore, this study will evaluate effectiveness of meeting recommended physical activity guidelines to maintain function and reduce disability for persons with arthritis. This is key information for the clinical management of these patients and for the design of public health programs to reduce arthritis-related disability. Findings from this study will advance public health efforts to improve quality of life among 48 million US adults having arthritis. This study will use the methodologically strong framework of a randomized clinical trial to determine if the Physical Activity Management (PAM) intervention reduces disability and improves the frequency at which persons with knee osteoarthritis (OA) and rheumatoid arthritis (RA) meet recommended physical activity guidelines. This study also measures the effect of attaining recommended public health guidelines to reduce disability progression and maintain function in knee OA and RA patients. This is key information for the clinical management of these patients and to advance public health efforts to improve quality of life among 48 million US adults having arthritis.